As a small force of Islamic State militants holds out in parts of Tikrit for a fourth week, Iraqi forces have been forced to shift tactics, officials say: Rather than storming in to clear the city at any cost, the security forces are trying to seal off the area and begin preparing for even more challenging battles to the west and north.

The Iraqi forces’ progress has put them closer to the doorstep of Nineveh Province, where the city of Mosul looms as the most important battle against the Islamic State. But the hard lessons of the Tikrit offensive, with a heavy cost in casualties for the Shiite militiamen and soldiers involved, have Iraqi officials thinking more cautiously about their next steps.

To that end, officials say, their next goal will be securing the western province of Anbar, in part to keep Islamic State fighters there from ambushing and harassing the main Iraqi force to the east. […]